With an increase in the packing density of LSIs, the required linewidths of circuits included in semiconductor devices become finer year by year. To form a desired circuit pattern on a semiconductor device, a method is employed in which a high-precision original pattern (i.e., a mask, or also particularly called reticle, which is used in a stepper or a scanner) formed on quartz is transferred to a wafer in a reduced manner by using a reduced-projection exposure apparatus. The high-precision original pattern is written by using an electron-beam writing apparatus, in which a so-called electron-beam lithography technique is employed.
As an electron beam writing apparatus, for example, a multi-beam writing apparatus is known, where radiation with a large number of beams is performed at a time using multiple beams to increase throughput. In the multi-beam writing apparatus, for example, electron beams emitted from an electron gun pass through an aperture member with a plurality of holes and multiple beams are formed consequently, and each beam undergoes blanking control on a blanking plate. The beams that have not been shielded are reduced through an optical system and a desirable position on a mask as a writing target is radiated with the resultant beams.
When electron beam writing is performed using a multi-beam writing apparatus, the layout of a semiconductor integrated circuit is designed first and design data is generated as layout data. By partitioning a polygonal figure included in the design data into a plurality of trapezoids, writing data to be input to the multi-beam writing apparatus is generated. With respect to each trapezoid, when one vertex serves as an arrangement origin point, the writing data includes coordinate data on the arrangement origin point and data indicating displacements from the arrangement origin point to the other three vertices.
When the design data includes a figure that is approximately presented by a polygonal figure having a large number of sides, such as an oval figure, the polygonal figure is partitioned into a large number of trapezoids. The data amount of the writing data is enormous since as regards each of the large number of trapezoids, the writing data includes the coordinate data on the arrangement origin point and the data indicating displacements from the arrangement origin point to the other three vertices.
To lessen the data amount of the writing data, a technique is proposed, by which a polygonal figure is partitioned into a plurality of trapezoid figures that each include at least one pair of opposite sides parallel along a first direction and join along a second direction orthogonal to the first direction while a side parallel to the first direction serves as a common side, and the position of a common vertex shared by a first trapezoid and a second trapezoid that adjoins the first trapezoid is represented using displacements in a first direction and a second direction from the position of a common vertex shared by the second trapezoid and a third trapezoid that adjoins the second trapezoid. According to this technique, the amount of one radiation (a dose amount) can be defined for each trapezoid.
As a phenomenon that causes variation in pattern dimension during electron beam writing, a proximity effect is known, which is unique to an EUV mask whose influence radius is exceedingly short like approximately 300 nm to 400 nm. When dose amount correction computing is performed while taking the effect into account, the computing needs to be performed on each of partitioned small regions, which are obtained through mesh partitioning for a writing region by approximately 30 nm to 100 nm for example.
According to the above-described conventional technique, even when the length of a trapezoid in the first direction is larger in size than a small region after the mesh partitioning, no more than one dose amount can be defined. It is thus difficult to perform the dose amount correction computing for inhibiting variation in pattern dimension.